Oak Harbor, WA rainwater: 20,434 gallons off a roof
How much rain a roof in Oak Harbor, WA collects
20,434gallons a year
That is a 1,500 sq ft asphalt roof under Oak Harbor, WA's normal 25.7 inches of rain, about 795 gallons for every inch that falls.
Oak Harbor, WA has gaps between storms long enough to drain a single barrel. Around 165 gallons of storage catches most of what is worth catching.
Rainfall: NOAA 1991-2020 climate normals, the Oak Harbor 1.1 Nnw station (0.9 mi away). Oak Harbor, WA ranks 72nd wettest of the 91 cities covered in Washington.
Month by month in Oak Harbor
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 3.32 | 2,639 | |
| Feb | 2.37 | 1,884 | |
| Mar | 1.98 | 1,574 | |
| Apr | 2.05 | 1,629 | 287 |
| May | 1.94 | 1,542 | 300 |
| Jun | 1.39 | 1,105 | 369 |
| Jul | 0.76 | 604 | 448 |
| Aug | 0.92 | 731 | 428 |
| Sep | 1.30 | 1,033 | 380 |
| Oct | 2.65 | 2,106 | 212 |
| Nov | 3.90 | 3,100 | |
| Dec | 3.13 | 2,488 |
Nov is the wettest month (3.90 in, 3,100 gal off the roof); Jul the driest (0.76 in). Garden shortfall is what a 200 sq ft vegetable bed needs beyond the rain that lands on it, April to October.
Barrel or cistern in Oak Harbor?
Best fit: 3 linked 55-gallon barrels, which delivers about 2,000 gallons to the garden in a normal year (82.5% of its need).
If you set one up, link barrels with a short hose at the base so they fill and drain together, and check the overflow points away from the house.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 1,259 | 18,215 |
| 110 gal | 1,769 | 17,706 |
| 165 gal | 2,000 | 17,475 |
| 275 gal | 2,126 | 17,348 |
| 550 gal | 2,126 | 17,348 |
| 1,000 gal | 2,126 | 17,348 |
| 1,500 gal | 2,126 | 17,348 |
| 2,500 gal | 2,126 | 17,348 |
| 5,000 gal | 2,126 | 17,348 |
Simulated storm by storm through a normal year using the station's count of days with 0.1 in or more of rain each month.
Is rainwater collection legal in Washington?
Collecting and storing rooftop rainwater for use on site needs no water right permit, provided the roof is part of a fixed above-ground structure whose primary purpose is not rain collection. Ecology may set local restrictions on new systems if they harm instream values or existing water rights. No state storage cap in the policy.
Checked against the current source on 2026-11-06. Source